Cognitive radio (CR) is the most promising technology to address spectrum resource shortage at present. By using the cognitive radio technology, frequency bands may be dynamically accessed under the premise that a primary user (PU) is not interfered, so as to improve spectrum utilization rate. At present, the Federal Communications Commission in the United States has officially released regulations to allow devices to access the television white spectrum (TVWS or TV white spectrum) under the premise that no interference is caused. In addition, as specified in standards such as Institute of Electrical and Electronics Engineers (IEEE) 802.22 being formulated by the Institute of Electrical and Electronics Engineers, the TVWS serves as a target frequency band of spectrum sharing.
Spectrum sensing is one of the core technologies of the cognitive radio, and an objective thereof is to find an idle spectrum not in use by radio spectrum detection, so as to provide the spectrum to a CR system for using. The spectrum sensing has two categories, namely, in-band sensing and out-of-band sensing, where the in-band sensing refers to sensing for spectrum being used by the CR system, and aims to exit the spectrum when a primary user signal occurs; and the out-of-band sensing refers to sensing for spectrum not used by the CR system, and aims to find the idle spectrum not in use. In order to avoid that data transmission of the CR system causes interference to spectrum sensing, the in-band sensing needs to be performed in a quiet period (QP). In the quiet period, the CR system cannot perform data transmission, so as to avoid interference. Therefore, the design of the quiet period not only guarantees the spectrum sensing performance, but also needs to consider the influence on the CR system due to transmission interruption.
In the IEEE 802.22, in-band sensing is performed by setting a specific quiet period in a radio frame. The spectrum sensing is performed in two quiet periods of intraframe sensing and interframe sensing. The position and the length of the quiet period are controlled by a base station, and are sent to a terminal. In the quiet period, the base station and the terminal stops receiving and sending of all data, and performs spectrum sensing. However, in this quiet period setting solution, it is required to reserve time in a frame structure for the quiet period specifically. If the setting method of the quiet period is introduced to an existing system, for example, a time-division long-term evolution (TD-LTE) system, an existing protocol needs to be changed greatly, which results in significant increase of the system complexity.